The invention relates to a portable measuring system with a small assembly space that can be used to analyze a liquid sample for at least one analyte contained therein. Measuring systems of this kind are used in particular in the field of medicine, for example, for blood glucose monitoring, or in the field of chemical or biological analysis, for example, environmental analysis.
Monitoring of blood glucose concentration is an essential part of the daily routine of diabetics. Blood glucose concentration must be determined quickly and reliably several times a day in order, if appropriate, to be able to take suitable medical measures. So as not to restrict the diabetic's daily routine any more than is necessary, suitable portable devices are often employed which are intended to be easy to carry and to operate such that the blood glucose concentration can be measured, for example, at the workplace or even during leisure time.
Various portable devices are presently available on the market, some of them functioning according to different measurement methods. Various diagnostic methods are used in these devices, for example, optical or even electrochemical measurement methods. An example of a frequently employed measurement method utilizes a special kind of electrochemical test strips. These test strips are, for example, configured such that a predetermined quantity of blood is conveyed to an electrode system via a capillary system on the test strip. For modern test strips, a quantity of blood of ca. 1.5 ml is sufficient, sometimes even quantities of blood of less than 1 ml can be used. The electrode system may, for example, involve gold electrodes that are provided with a coating. The coating in most cases contains different enzymes and so-called mediators and has the effect that charge carriers (for example in the form of redox molecules) form within the sample on the electrodes, the concentration of these charge carriers being dependent on the blood glucose concentration. The concentration of these charge carriers can be determined by means of the gold electrodes and a suitable measurement system, for example, by means of a current-voltage measurement, and from this concentration it is possible, finally, to calculate the blood glucose concentration. An example of electrochemical test strips of this kind is set out in U.S. Pat. No. 5,286,362.
As an alternative to the electrochemical measurement method described above, other measurement principles can also be used. Thus, for example, Publication No. WO 01/48461 describes a test strip with light guides for examining a sample, in particular, of a body fluid, in which a reagent system, upon reaction with the sample, leads to a characteristic and optically measurable change in a detection zone. By way of light guides that are let into the test strip, this change can be evaluated by an evaluation device.
The test strips thus form an important element of portable diagnostic systems. Typically, about 5 to 7 of such test strips are needed each day by a diabetic. It is essential that the test strips are stored in a clean and dry condition to ensure that the measurement of the blood glucose concentration is not rendered inaccurate by contamination or by the effect of moisture.
For this purpose, the test strips are usually stored in suitable containers in order to then be removed by the user from the test strip container for a measurement and fitted into a corresponding measuring device. Such measuring devices, for example, measuring devices for electrochemical or optical determination of the blood glucose concentration, are known to persons skilled in the art and described, for example, in US Patent Publication No. 2002/0170823 A1.
For storing and dispensing the test strips, magazine systems are also known. For example, US Patent Publication No. 2003/0116583 A1, EP 0 640 393 and U.S. Pat. No. 4,911,344 describe suitable storage systems in which several test strips are stored in a magazine. EP 1 488 736 also describes a system which contains, instead of individual test strips, a tape cassette composed of a long individual test strip with a plurality of test fields.
In addition to systems in which the test strip magazine and measuring device are used as separate units, integrated systems also exist which not only comprise several test strips stored in one magazine, but also afford the possibility of evaluation of these test strips. Examples of systems of this kind are to be found in U.S. Pat. No. 5,489,414, U.S. Pat. No. 6,093,156, and Publication Nos. WO 02/18940, WO 02/055008 or WO 03/083469. Some of these systems, for example the system described in U.S. Pat. No. 6,093,156 or Publication No. WO 03/083469, already comprise an integrated lancet system too, which makes it possible to perforate the skin to generate a blood droplet and then permits analysis of the blood droplet using one and the same measuring system.
However, in the systems known from the prior art, the problem surrounding moisture sensitivity, of the test strips has only been partially solved. Thus, for example, German Patent No. DE 103 32 488 and US Patent Publication No. 2005/0033196 each disclose test systems with integrated lancet system and test strips, in which blood droplets are applied directly to test strips. In these cases, however, the test strips are largely unprotected and thus exposed to the air moisture.
Air moisture, especially at elevated temperatures and over long periods of time, can affect the sensitivity of the test strips and thus render the measurement inaccurate. To avoid this, the systems disclosed in Publication Nos. WO 03/083469 or WO 02/055008, for example, contains separate, exchangeable, airtight test strip magazines, which are inserted into the actual measuring device. However, this requires dual packaging of the test strips, which requires considerable assembly space, since the test strips are now surrounded by the actual magazine wall as primary packaging and in addition by the wall of the measuring device. Analogously, Publication No. WO 2006/047135 also describes a complex test strip dispenser with a test strip “cartridge.” Here, a device housing encloses a magazine (cartridge), which for its part has an outer envelope and an inner envelope. The test strips are stored in a moisture-proof manner in the magazine. Since optimization of size is a crucial factor for portable medical measuring devices, the disadvantage of the dual packaging of the systems known from the prior art is in some cases critically important when it comes to the patient's acceptance of the measuring device.
Other systems, for example, the system disclosed in U.S. Pat. No. 5,489,414, are based on individually sealed test elements. These test elements can be designed, for example, as multi-use test elements with individually sealed test areas. A disadvantage of these, however, is that the seal of the test elements has to be removed before use, which requires additional mechanical action, for example, or manual action on the part of the patient. Automatic removal of the seal, for example by perforation of the seal, requires additional mechanical elements and drive elements inside the measuring device, which in turn greatly increases the assembly space and/or the energy requirement of the systems.
These examples show that it has not hitherto been possible to entirely solve the problems of, on the one hand, ensuring that disposable test elements for reloading of the measuring devices can be transported to the measuring device in an airtight package or seal (for example commercially) and, on the other hand, of ensuring that these sealed test elements can then be used in the measuring device itself with removal of the seal.